This invention relates to transfer apparatus and method and more particularly to a transfer apparatus and method that reduces or substantially eliminates adverse effects of vacuum holes on pneumatically constrained paper transported through a transfer zone.
In reproduction processes, such as in the process of xerography, wherein a latent image is formed on an electrostatic member and then made visible, or developer, with a powderous material, the electrostatic member can be used repeatedly to form additional images in successive cycles if the developed image is transferred from it to another substrate such as a copy sheet during each cycle. When the xerographic process is employed, the electrostatic member can take the form of a photoconductive layer over a conductive backing material. The photoconductive layer is given a uniform electrostatic charge and then exposed to a light image conforming to the information to be reproduced to form a latent electrostatic image on the member. The member is then developed with a finely divided, pigmented, electroscopic resinous powder called toner and the toner image is then transferred to a copy sheet. After transfer is complete, the surface of the electrostatic member can be cleaned and the reproduction process started again, if desired.
The most desirable aspects of a transfer apparatus are high transfer efficiency with no image defects and high reliability, including insensitivity to external machine variables (relative humidity, paper type, etc.) where both are achieved with minimum complexity and cost. Transfer systems in the past that included pneumatically constrained paper transport through the transfer zone had the disadvantage of being unable to achieve all of the above desirable features because of printout of the vacuum holes located within the transport member on the copy resulting from, for example, a distortion of the electrostatic fields. Prior art devices that disclosed the use of a vacuum source in conjunction with a transport conveyor to transport sheets through a transfer zone includes U.S. Pat. No. 3,647,292 and U.S. Pat. No. 3,832,053.
Accordingly, it is an object of this invention to improve transfer so as to eliminate or substantially reduce the adverse effects of vacuum hole printout in pneumatically constrained paper.
It is a further object of this invention to present a continuously contrasting pattern of vacuum holes within the transfer zone to counteract vacuum hole printout.
It is a still further object of this invention to improve transfer regardless of machine variables.